The DNA Synthesis Resource Core plays an essential role in the successful integration of this Program Project by providing high purity, site-specifically modified oligonucleotides to Projects 1, 2 and 3. The DNA Synthesis Resource Core works closely with Project 1, where novel reagents and synthetic strategies are developed for the site-specific synthesis of oligonucleotides containing the Fapy-dG lesions of interest to the Program ProjecL The technology is transferred to the Core, where the desired modified oligonucleotides are synthesized on the appropriate scale and purity for further chemical and replication studies by Project 1, cell-based studies by Project 2, and structural studies by Project 3. The Specific Aims for the DNA Synthesis Resource Core are: 1) to synthesize the phosphoramidite reagents of the various Fapy-dG lesions and Incorporate them into oligonucleotides; 2) develop protocols for the purification of the modified oligonucleotides; and 3) provide initial characterization of modified oligonucleotide.